The presence of connective interstitial cells in the wall of several organs of the distal reproductive system in Oxychilus atlanticus is described by means of scanning electron microscopy (SEM). Connective interstitial
cells extend from the distal part of the vas
deferens to the penis, being the dominant cell type of large portions of the epiphallus as well as in the whole penial caecum (flagellum). These cells are highly mineralized and are characterized by the presence of large amounts of solid spherules (up to 4 m in diameter) in their cytoplasm. A semi-quantitative evaluation by X-ray microanalysis demonstrates that
calcium and phosphorus are the main elements of the spherules. Their function is unknown, but they could aid in copulation or they could assist the survival of the transferred spermatozoa.